There's no such thing as a 6 thousandths overbore. The first oversize that's commonly done is a 30 thousandths (.030"), and the second overbore is usually 40 or sometimes 60. 250's are very bad about getting major wear on the #1 cylinder due to oddball coolant flow, so it's not uncommon to have to rebore to a big oversize, or to have to put a sleeve in the #1 cylinder to get it back to an acceptable size. If you put standard diameter rings in 60 over cylinders, they would almost fall in without using a piston ring compressor, and there would be no way to keep the engine from smoking. Sound familiar?
Jerry
